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United States Patent |
5,024,865
|
Insley
|
June 18, 1991
|
Sorbent, impact resistant container
Abstract
An article comprising compressed particles of polyolefin microfibers is
provided. The article has a solidity of at least 20% is particularly
suitable as a container for shipping and storing hazardous liquid
materials or a cryogenic container.
Inventors:
|
Insley; Thomas I. (Lake Elmo, MN)
|
Assignee:
|
Minnesota Mining and Manufacturing Company (St. Paul, MN)
|
Appl. No.:
|
593308 |
Filed:
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October 2, 1990 |
Current U.S. Class: |
428/36.4; 206/204; 220/901; 428/36.5; 428/76; 428/218; 428/220; 428/372; 428/903; 428/913 |
Intern'l Class: |
B32B 023/02 |
Field of Search: |
428/36.4,36.5,68,76,92,218,220,327,357,364,372,402,903,913
206/204,523,443
220/901
|
References Cited
U.S. Patent Documents
Re24767 | Jan., 1960 | Simon et al. | 206/46.
|
2929425 | Mar., 1960 | Slaughter | 150/1.
|
2941708 | Jun., 1960 | Crane et al. | 229/2.
|
3309893 | Mar., 1967 | Heffler et al. | 62/372.
|
3698587 | Oct., 1972 | Baker et al. | 220/9.
|
3895159 | Jul., 1975 | Yoshimura | 428/227.
|
3971373 | Jul., 1976 | Braun | 128/146.
|
3981100 | Sep., 1976 | Weaver et al. | 47/58.
|
3999653 | Dec., 1976 | Haigh et al. | 206/584.
|
4100324 | Jul., 1978 | Anderson et al. | 428/288.
|
4118531 | Oct., 1978 | Hauser | 428/224.
|
4124116 | Nov., 1978 | McCabe, Jr. | 206/204.
|
4213528 | Jul., 1980 | Kreutz et al. | 206/205.
|
4240547 | Dec., 1980 | Taylor | 206/204.
|
4426417 | Jan., 1984 | Meitner et al. | 428/195.
|
4429001 | Jan., 1984 | Kolpin et al. | 428/283.
|
4481779 | Nov., 1984 | Barthel | 62/48.
|
4495775 | Jan., 1985 | Young et al. | 62/48.
|
4560069 | Dec., 1985 | Simoa | 206/991.
|
4584822 | Apr., 1986 | Fielding et al. | 53/452.
|
4756937 | Jul., 1988 | Mentzer | 428/36.
|
4813948 | Mar., 1989 | Insley | 604/366.
|
Other References
Wente, Van A., "Superfine Thermoplastic Fibers", Industrial Engineering
Chemistry, vol. 48, pp. 1342-1346.
Wente, Van A., et al., Manufacture of Superfine Organic Fibers, Report. No.
4364, Naval Research Laboratories, published May 25, 1954.
Shock Control, Arimond, John, Machine Design, May 21, 1987.
|
Primary Examiner: Robinson; Ellis P.
Assistant Examiner: Turner; Archene A.
Attorney, Agent or Firm: Griswold; Gary L., Kirn; Walter N., Truesdale; Carole
Parent Case Text
This is a continuation of application Ser No. 07/335,202 filed Apr. 7, 1989
.
Claims
I claim:
1. A container having structural rigidity, impact resistance, providing
cushioning and absorbency properties comprising compressed particles of
polyolefin microfibers, said container having a solidity of at least 20%
and less than about 80%.
2. The container of claim 1 wherein said microfibers have a diameter of
less than about 50 microns.
3. The container of claim 1 wherein said microfibers have a diameter of
less than about 25 microns.
4. The container of claim 1 wherein said particles have an average diameter
of less than about 2 cm.
5. The container of claim 1 wherein said particles have an average diameter
of less than about 1 cm.
6. The container of claim 1 wherein said polyolefin microfibers are
polyethylene, polypropylene, polybutylene, blends thereof, copolymers of
ethylene, copolymers of propylene, copolymers of butylene or blends of
said copolymers.
7. The container of claim 1 wherein said article has a solidity of at least
about 30%.
8. The container of claim 1 wherein said microfibers are divellicated or
milled meltblown.
9. The container of claim 1 wherein said microfibers are in the form of
microfiber microwebs.
10. The container of claim 9 wherein said article has a solidity of about
40 to 50%.
11. The container of claim 1 wherein said article has a demand sorbency of
at least about 0.5 1/m.sup.2 /min.
12. The container of claim 1 wherein said article has a demand sorbency of
at least about 1.0 1/m.sup.2 /min.
13. The container of claim 1 wherein said article has an equilibrium
sorption of at least about 0.25 cm.sup.3 /cm.sup.3.
14. The container of claim 1 wherein said article has an equilibrium
sorption of at least about 0.40 cm.sup.3 /cm.sup.3.
15. The container of claim 1 wherein said article has a centrifugal
retention of at least about 0.15 cm.sup.3 /cm.sup.3.
16. The container of claim 1 wherein said article has a tensile strength of
at least about 9 KPa.
17. The container of claim 1 wherein said article has a tensile strength of
at least about 20 KPa.
18. The container of claim 1 wherein said article has a strain energy of at
least about 5 KJ/m.sup.3.
19. The container of claim 1 wherein said article has a strain energy of at
least about 20 KJ/m.sup.3.
20. The container of claim 1 wherein said article has a thermal
conductivity of less than about 1.0.times.10.sup.-4 cal/cm-sec-.degree. C.
at a temperature of 76.degree. C.
21. The container of claim 1 wherein said article s a thermal conductivity
of less than about 1.5.times.10.sup.-4 cal/cm-sec-.degree. C. at a
temperature of 76.degree. C.
22. The container of claim 1 further comprising a sorbent particulate
material.
23. The container of claim 1 further comprising a neutralizing particulate
material.
24. The container of claim 1 further comprising a catalytic agent.
25. The container of claim 1 wherein said article is a container for
storing or shipping hazardous liquid materials.
26. The container of claim 1 further comprising an impermeable protective
outer layer.
27. A process for preparing an article comprising the steps of
i) divellicating or milling a polyolefin microfiber web to provide
particles of polyolefin microfibers,
ii) providing said particles to a mold,
iii) applying pressure to said microfibers,
iv) releasing said pressure, and
v) removing said article from said mold, said pressure being sufficient to
achieve a solidity of at least about 20% when said pressure is released.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a container which is useful for shipping
and storing hazardous fluid materials.
2. Background Information
The shipment of hazardous fluid materials requires the use of a shipping
container or package which will protect the vessel holding the material
from shock which can cause breakage as well as provide for containment or
control of the fluid material should the vessel be broken. The shock
protection and containment requirements are generally incompatible in that
materials which provide good shock protection typically exhibit poor fluid
containment or absorption properties and materials having good fluid
containment or absorption properties exhibit poor shock protection
properties. Hazardous fluid material shipping containers which offer both
shock and containment protection which have evolved are a combination of a
more rigid container which provides shock protection that is filled with
an absorbent material. This combined structure results in a shipping
package that is very large relative to the volume of hazardous material
being shipped in the package.
Simon U.S Pat. No. 4,560,069 discloses a package assembly for transporting
hazardous materials including a bottle containing the hazardous material
disposed within a metal can wherein the bottle is surrounded on all sides
by individual upper, lower and side absorbent non-resilient and frangible
synthetic foam elements. The foam elements provide cushioning for the
bottle and absorbency in the case of spillage. The individual foam
elements are maintained out of contact with each other by means of a
fiberboard spacers. The spacers are disposed to separate the upper and
lower ends of the bottle from the resin foam and to protect the frangible
foam from disintegration due to abrasion by the bottle. The metal can can
be suspended within an outer corrugated fiberboard box by means of a
fiberboard insert element for the outer box. The fiberboard insert element
supports the can out of contact with the outer fiberboard box and provides
a protecting buffer zone between the can and the walls of the outer
fiberboard box for protection of the can.
Haigh et al. U.S Pat. No. 3,999,653 discloses a package containing a
hazardous liquid which comprises a container which is generally
impermeable to a hazardous liquid contained therein, the container being
subject to discharge of its contents when subjected to impact. The
container is disposed within a first jacket of a liquid permeable material
of sufficient strength to contain fragments of the container on rupture
thereof. A second jacket is provided over the first jacket, the second
jacket having at least an inner wall and outer wall, the inner wall being
liquid permeable, a hazardous liquid swellable body contained between the
inner wall and outer wall and being generally co-extensive with the inner
wall and outer wall, and a third jacket of hazardous liquid vapor
imperious membrane.
Kreutz et al. U.S. Pat. No. 4,213,528 discloses a package for an acid
container, such as an acid containing ampule or bottle, formed of an acid
resistant envelope and a separate removable absorbent shield for enclosing
the acid container, with the absorbent shield including a material to
neutralize acid whereby any acid released from the container is absorbed
and neutralized by the absorbent shield. The absorbent shield is generally
porous, yet sufficiently absorbent to allow essentially instantaneous
absorption of acidic liquids of high, medium and low viscosities.
Simon et al. U.S. Patent No. Re 24,767 discloses a packaging container that
provides uniform thermal, shock, impact, vibration, inertia and fluid
impervious insulation for a fragile or delicate object or material. The
object or material is completely encased in a yielding, flexible and
resilient cellular or foamaceous sheath of selected thickness that is
effective as a protection against shock, impact, vibration, inertia
effects, etc. as well as being a good thermal insulating blanket, the
sheath cradling and supporting the object or material, and a fluid-tight
or impervious shell to protect the object or material against
deterioration by temperature changes or moisture.
Slaughter U.S. Pat. No. 2,929,425 discloses a protective pouch comprising
an elongated cushioning strip having a series of pockets into which parts
to be packaged may be inserted. The pouch is so constructed that one or
more of the longitudinal edges of the cushioning strip may be folded over
the pockets to cover them, and then the pouch is either rolled up or
folded up for insertion into a shipping container such as a metal can, a
wooden box or a carton.
Crane et al. U.S. Pat. No. 2,941,708 discloses a molded pulp set-up
insulating container in which six integrally joined sections have rims
disposed thereon to give locking contact where free section edges meet.
The container is molded so as to have the minimum amount of pulp in direct
contact with the goods held in the container to minimize heat transfer
through the pulp. The container has sufficient rigidity to support the
goods within the container and to also entrap a blanket of insulating air
around the goods.
Heffler et al U.S. Pat. No. 3,309,893 discloses an insulated shipping
container which has an elongated body, quadrilateral in cross section,
formed of a rigid, inflexible polyurethane foam, having a
heat-conductivity factor in the range of 0.11 to 0.20 and integrally
provided with a cavity of circular cross section opening at one end of the
body and being closed at its other end and a closure for the cavity being
of cylindrical form and having a diameter greater than that of the cavity
and formed of resilient, flexible, and porous polyurethane foam for
sealing engagement within the open end of the cavity for forming a tight
joint with the walls thereof while permitting the escape of gases from
within the container and having a heat conductivity factor in the range of
0.22 to 0.35.
Baker et al U.S. Pat. No. 3,698,587 discloses a self-sealing wall for
containers and conduits comprising a substantially rigid supporting layer
of liquid impervious material, a layer of foam and at least one layer of a
homogeneous elastomeric polyurethane adhered to the foam.
Yoshimura U.S. Pat. 3,895,159 discloses a cryogenic insulation material
which is shaped in conformance with the form of an article to be insulated
and is made of a rigid polyurethane foam having a core layer including
cells and inner and outer surface layers including hardly any cells. Glass
fiber is embedded at least in the inner surface layer.
McCabe, Jr. U.S. Pat. No. 4,124,116 discloses a liquid absorbing sectional
pack consisting of upper and lower filter sheets bonded to each other at
the outermost contiguous edges to form an enclosure. The enclosure is
divided into a plurality of sectional compartments which are isolated from
each other by dissolving barrier sheets. The dissolving barrier sheets
consist essentially of a water soluble carboxy methyl cellulose compound.
Each of the sectional compartments contain a predetermined quantity of
absorbent granules. The barrier sheets function to dissolve when the
granules have absorbed a predetermined amount of moisture so as to provide
for increased space in which to contain moist granules.
Taylor U.S. Pat. No. 4,240,547 discloses a compact, reusable specimen
mailer for safely shipping fragile specimen containers via the postal
service. Two substantially identical L-shaped matable parts are each
provided with a long leg having a flat free end and a flat inside face,
and a short leg having a flat inside face, so that the two parts may be
joined together with the free end of the long legs of the two parts flush
against each other. Typically, the long leg of each part forms apertures
for receiving test tubes, which protrude from the free end of the long leg
of the other part. Also typically, the long leg forms an aperture opening
out of its free end and its inside face, and connected with another cavity
formed in the inside face of the short leg, for receiving a slide holder.
A sheet of absorbent material is disposed within a recess in the inside
face of the long leg for absorbing leaking fluids. The two parts are
joined together and placed in a special envelope for mailing.
Barthel U.S. Pat. 4,481,779 discloses a storage container for shipping
transportable materials at cryogenic temperatures including a vessel which
opens to the atmosphere and contains a micro-fibrous structure for holding
a liquefied gas such as liquid nitrogen in adsorption and capillary
suspension. The micro-fibrous structure comprises a core permeable to
liquid and gaseous nitrogen and an adsorption matrix composed of a web of
inorganic fibers surrounding the core in a multi-layered arrangement.
Young et al U.S. Pat. 4,495,775 discloses a container for shipping
transportable materials at cryogenic temperatures including a vessel which
opens to the atmosphere and contains a micro-fibrous structure for holding
a liquefied gas such as liquid nitrogen in adsorption and capillary
suspension. The micro-fibrous structure comprises a core permeable to
liquid and gaseous nitrogen and an adsorption matrix composed of randomly
oriented inorganic fibers surrounding the core as a homogeneous body in
stable confinement.
Fielding et al U.S. Pat. No. 4,584,822 discloses a cushion packing material
for use in protecting objects from shock and vibrational loads. The
cushion packing comprises a dimensionally stable thermoformed shell
forming a chamber therein of a predetermined configuration and having a
foam material, preferably low density polyurethane foam, disposed
therewithin so as to provide a molded density of less than or equal to 1.5
pounds per cubic foot.
SUMMARY OF THE INVENTION
The present invention, in one aspect, provides an article comprising
compressed particles comprising polyolefin microfibers, said article
having a solidity of at least 20%.
The present invention, in another aspect, provides a container comprising a
shaped article of compressed particles of polyolefin microfibers, said
article having a solidity of at least about 20%. The container is
absorbent, impact resistant and thermally insulating. Preferably, the
container is enclosed in an impermeable protective outer layer.
Particulate and other fibrous material can also be incorporated in the
compressed particles of polyolefin microfiber structure. The container has
excellent structural rigidity, impact resistance, and compression
resistance and provides both excellent cushioning properties and excellent
sorbency.
The container is particularly useful for storing and transporting hazardous
liquid materials such as acidic materials, caustic materials, and
biological fluids, particularly when such materials are packaged in
breakable vessels. Generally, the preferred material for containment of
hazardous liquid materials are rigid breakable materials such as glass or
high density thermoplastic materials such as polyolefin, polycarbonate or
polyester in the form of jars, bottles, vials, or test tubes. In handling
and shipping, such vessels are susceptible to breakage through impact.
Breakage of the vessel creates the potential for contamination of the
surrounding environment and the potential human risk associated in
contacting the contaminated broken vessel and its contents. The excellent
cushioning and sorbency properties of the containers of this invention
provide an excellent means for safely storing and shipping hazardous
liquid materials in breakable vessels.
The container of the present invention is also useful for storing and
shipping materials under cryogenic conditions.
The container of the present invention also can provide excellent thermal
insulation for vessels stored and shipped in the containers.
The present invention, in a further aspect, provides a process for
preparing the compressed particles of polyolefin microfiber article of the
present invention comprising providing particles of polyolefin microfibers
to a mold, applying pressure to said particles, releasing said pressure,
and removing said article from said mold, said pressure being sufficient
to achieve a solidity of at least about 20% when said pressure is
released.
The present invention, in another aspect, provides a process for preparing
a container comprising providing particles of polyolefin microfibers to a
mold, applying pressure to said particles to form said container,
releasing said pressure, and removing said container from said mold, said
pressure being sufficient to achieve a solidity of at least about 20% when
said pressure is released.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a container of the present invention.
FIG. 2 is a perspective view of another container of the present invention.
FIG. 3 is a perspective view of a further container of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
The polyolefin fibers useful in the present invention can be formed from
polyethylene, polypropylene, polybutylene, blends thereof and copolymers
of ethylene, propylene and/or butylene. The fibers are preferably less
than about 50 microns, more preferably less than about 25 microns, most
preferably less than about 10 microns, in diameter. The fibers are
preferably prepared by melt blowing, flash spinning, or fibrillation.
Particularly preferred are blown microfibers in web form which has been
milled or divellicated to form the particles of polyolefin microfibers.
The particles preferably are less than about 2 cm, more preferably less
than about 1 cm, most preferably less than about 0.5 cm in average
diameter, although a small amount, generally less than about 5 weight
percent can range in size up to about 10 cm.
The microfiber webs can be prepared, for example, as described in Wente,
Van A., "Superfine Thermoplastic Fibers," Industrial Engineering
Chemistry, vol. 48, pp. 1342-1346, and in Wente, Van A. et al.,
"Manufacture of Superfine Organic Fibers," Report No. 4364 of the Naval
Research Laboratories, published May 25, 1954, or from microfiber webs
containing particulate matter such as those disclosed, for example, in
Braun U.S. Pat. No. 3,971,373, Anderson et al U.S. Pat. No. 4,100,324 and
Kolpin et al. U.S. Pat. No. 4,429,001, which are incorporated herein by
reference.
The microfiber webs are then formed into particles having a size of less
than about 2 cm average diameter such as by, for example, milling or
divellicating. Milling can be carried out using a hammer mill, a cryogenic
mill or a shredder. Divellicating can be carried out using a lickerin as
described in Insley U.S. Pat. No. 4,813,948 which is incorporated herein
by reference. Such divellicating produces microwebs having a relatively
dense nucleus with fibers and fiber bundles extending therefrom. The
nucleus of the microfiber microwebs is preferably in the range of about
0.05 to 4 mm, more preferably about 0.2 to 2 mm. The extending fibers
and/or fiber bundles preferably extend beyond the nucleus to provide an
overall diameter of about 0.07 to 10 mm, more preferably about 0.1 to 5
mm.
The articles and containers of the invention are formed by compressing the
particles of polyolefin microfibers, i.e., the microfiber microwebs to a
solidity of at least about 20%, preferably at least about 30%. The
solidity of the article or container is calculated according to the
formula
##EQU1##
When the solidity is less than about 30%, the shaped article may require
support, i.e., plastic casing, fiberboard box, or metal outer casing.
Preferably, the polyolefin fibers are compressed to a solidity of less
than about 80%, more preferably less than about 70%. When the solidity is
greater than about 80%, the sorbency and cushioning properties of the
shipping container may be insufficient. When the polyolefin fibers are
provided as microfiber microwebs, the solidity of the article is most
preferably about 40 to 50% which provides a material which can be drilled
or milled to the desired shape and has excellent sorbency and cushioning
properties.
Compression of the particles of polyolefin microfibers can be accomplished
using conventional compression molding equipment such as, for example,
flash molding, or powder molding equipment at ambient conditions.
Generally, pressures in the range of about 2 to 25 MPa are sufficient to
achieve the desired degree of solidity. When the particles are microfiber
microwebs, pressures in the range of about 5 to 10 MPa can preferably be
used to achieve the preferred solidity of about 40 to 50%. Although such
pressures are used to compress the particles of microfibers to form the
articles of the invention, there is no significant fusing of the
microfibers and no reduction in the available microfiber surface area.
The articles and containers of the invention have excellent sorbency. The
articles and containers preferably exhibit a demand sorbency of at least
about 0.5 1/m.sup.2 /min, more preferably at least about 1.0 1/m.sup.2
/min, most preferably at least about 2.0 1/m.sup.2 /min. The articles and
containers preferably exhibit an equilibrium sorption of at least about
0.25 cm.sup.3 /cm.sup.3, more preferably at least about 0.40 cm.sup.3
/cm.sup.3, most preferably at least about 0.60 cm.sup.3 /cm.sup.3. The
articles and containers preferably exhibit a centrifugal retention of at
least about 0.15 cm.sup.3 /cm.sup.3, more preferably at least about 0.20
cm.sup.3 /cm.sup.3.
The articles and containers of the invention possess good mechanical
properties. The tensile strength of the article or container material is
preferably at least about 9 KPa, more preferably at least about 20 KPa,
most preferably at least about 50 KPa. The compressive strain energy of
the article and container material is preferably at least about 5
KJ/m.sup.3, more preferably at least about 20 KJ/m.sup.3, most preferably
at least about 40 KJ/m.sup.3.
The containers of the invention have excellent insulation properties, The
containers preferably have a thermal conductivity of less than about
1.5.times.10.sup.-4 cal/cm-sec-.degree. C., more preferably less than
about 1.0.times.10.sup.-4 cal/cm-sec .degree. C. at a temperature of
76.degree. C.
The containers of the invention can serve as containers for storing and
shipping materials under cryogenic conditions when imbibed with liquid
nitrogen. Preferably the outside of the container is provided with
insulation to reduce evaporation of the liquid nitrogen.
Particulate and fibrous material can be introduced into the compressed
polyolefin microfiber structure by introducing particulate or fibrous
material into the microfiber web as it is being formed as described in
Braun U.S. Pat. No. 3,971,373, Hauser U.S. Pat. No. 4,118,531, Anderson et
al U.S. Pat. No. 4,100,324 Kolpin et al. U.S. Pat. No. 4,429,001 which are
incorporated herein by reference, or by mixing the particulate or fibrous
material with the milled or divellicated microfibers prior to compression.
Preferably, the particulate is introduced into the microfiber web as it is
being formed.
Particulate materials useful in the present invention include, but are not
limited to absorbent particulate materials, neutralizing particulate
materials and catalytic agents. Preferably, the amount of particulate
incorporated in the compressed microfiber structure is less than about 90
weight percent, more preferably less than about 75 weight percent, most
preferably less than 50 weight percent.
Absorbent particulate materials useful with aqueous hazardous liquids
include high sorbency liquid sorbent particles such as, for example,
water-insoluble modified starches such as, for example, those sorbent
particulates described in U.S. Pat. No. 3,981,100, and high molecular
weight acrylic polymers containing hydrophilic groups. Among sorbent
particulate materials useful for sorbing liquids other than water are
alkylstyrene sorbent particles, such as Imbiber Beads.sup..TM., available
from Dow Chemical Company. Other sorbent particulate materials include
wood pulp and activated carbon, the activated carbon being particularly
useful for absorbing vapors which might evolve from the hazardous
material.
Neutralizing particulate materials useful in the present invention include,
for example, materials such as alumina, sodium carbonate, sodium
bicarbonate, calcium carbonate, etc Catalytic particulate materials which
can be introduced into the compressed polyolefin microfiber structure
include, for example, hopcalite and silver. Biological entities such as
enzymes or microbiological species which can catalyze the conversion of a
hazardous material into harmless by-products can also be incorporated into
the articles and containers of the present invention.
Preferably, the container of the present invention includes an outer
covering. The outer covering can be, for example, of fiberboard, metal, or
thermoplastic material. The preferred outer covering material is
shrinkable thermoplastic film which is well known in the art and can
provide an additional, impervious layer to further ensure containment of
the hazardous material.
The containers of the present invention can be molded and, optionally,
milled or drilled to a wide variety of shapes such that a package of
hazardous material can be safely stored or shipped in the container. The
size of the container is preferably such that there is sufficient sorptive
microfiber and particulate, if present, to absorb, contain, or neutralize
the hazardous material with some margin of safety.
FIG. 1 shows a preferred container 10 of the invention encasing a bottle 12
of hazardous liquid. Container 10 has a lower section 14 and a lid 16,
each of which are formed of compressed polyolefin microfibers. Lid 16 has
a protruding portion 18 which snugly fits the cavity 22 of lower section
14. A covering of shrinkable thermoplastic film 20 is provided around the
compressed polyolefin microfibers.
FIG. 2 shows a container 26 of the invention adapted for storage of test
tubes. Such a container is preferably molded as a block and then apertures
28 are drilled in the block for accommodating the test tubes.
FIG. 3 shows a container 30 adapted for containing vials of hazardous
liquid material. The container has a base 32 and a lid 34 of compressed
polyolefin microfibers. Such a container is preferably molded as a block
and base apertures 36 and lid apertures 38 are drilled into the block for
accommodating vials 40.
The following examples further illustrate this invention, but the
particular materials and amounts thereof in these examples, as well as the
conditions and details, should not be construed to unduly limit this
invention. In the examples, all parts and percentages are by weight unless
otherwise specified.
The following test methods were used to characterize the molded materials
of the invention:
Demand Sorbency Test
A 4.45 cm (1.75 inch) in diameter test sample of sorbent material was
placed on a 25-50 micron porous plate in a filter funnel and a pressure of
1.0 KPa applied to the sample by a plunger which was freely movable in the
barrel of the funnel. Deionized water at zero hydrostatic head was
conducted from a reservoir through a siphon mechanism to the upper surface
of the porous plate where the test sample sorbed the water. The initial
lineal rate of absorbency was determined and reported in 1/m.sup.2 /min.
Equilibrium Sorption
A sample of sorbent material was placed in a bath of deionized water and
allowed to saturate for 24 hours. The sample was then removed from the
bath and placed on an open mesh screen for 10 minutes to allow for
drainage of excess water. The amount of water sorbed by a unit volume of
material was determined and the equilibrium sorption reported in cm.sup.3
/cm.sup.3.
Centrifugal Retention Test
A sample of sorbent material, saturated to equilibrium (24 hr saturation
time) with deionized water, was placed in a centrifuge tube which was in
turn placed in a centrifuge and the sample subjected to a centrifugal
force of 180 G for 10 minutes. The sample was removed from the centrifuge
tube and the amount of water retained in the sample determined.
Centrifugal retention values are reported in terms of the volume of water
retained per unit volume of material (cm.sup.3 /cm.sup.3).
Mechanical Properties--Tensile Strength
Dog-bone shaped test specimens are molded having a total surface area of
66.8 cm.sup.2 and a test area of 25.5 cm.sup.2. The molded test specimens
(face width 2.5 cm; length 10.2 cm) were tested for maximum tensile
strength using an Instron Tensile test unit. Evaluations were conducted
using a X-head speed of 1.0 cm/min in accordance with ASTM F152- 86 Method
C.
Mechanical Properties--Compressive Stress/Strain Evaluations
Cylindrical specimens of 4.4 cm in diameter were subjected to compressive
stress using a Instron test unit incorporating a compression load cell.
The deflection of the specimen, for a given load, was recorded using a
uniform loading rate up to an ultimate loading of 689.5 KPa. The X-head
speed of the test unit during the evaluation was 1.0 cm/min. Strain energy
of the test specimen was determined by calculating the area under the
stress/strain curve and is reported in KJ/m.sup.3.
Thermal Conductivity
Thermal conductivity analysis conducted under ASTM F-433 were performed on
5.1 cm diameter cylindrical specimens of 1.3 cm in height and are reported
in cal/cm-sec-.degree. C.
Impact Energy Density
The impact energy density was determined according to ASTM Test Method
D-3331.
Cushioning Efficiency
The cushioning efficiency is determined as described in "Shock Control,"
Arimond, John, Machine Design, May 21, 1987. In this test, a 10 Kg weight
is dropped from varying distances onto a given volume of material and the
deceleration-time response is determined.
Surface Area
Surface area determination were conducted using BET nitrogen adsorption
method.
Carbon Tetrachloride Vapor Adsorption
A sample of sorbent material, preconditioned at 100.degree. C. in a
convection oven for 4 hours, was placed in a sealed dissector containing
carbon tetrachloride on a porous ceramic plate positioned about 2 cm above
the level of the carbon tetrachloride. Weight gain of the sample is
determined gravimetrically after exposure to the vapor for 24 hours.
EXAMPLE 1
A melt blown microfiber web was prepared as described in Wente, Van A.,
"Superfine Thermoplastic Fibers," Industrial Engineering Chemistry, vol.
48, pp. 1342-1346 using polypropylene resin (Dypro.sup..TM. 50 MFR,
available from Fina Oil & Chemical Co.,). The fibers were sprayed with a
surfactant solution (Aerosol.sup..TM. OT, available from American Cyanamid
Co.) at a rate to provide 2 percent surfactant based on the weight of the
fibers. The microfibers were about 6 to 8 microns in average diameter. The
web had a basis weight of 270 g/m.sup.2, a density of 5.2.times.10.sup.-2
g/cm.sup.3, a solidity of 5.7%, and a void volume of 18.1 cm.sup.3 /g. The
web was tested for sorbency properties. The results were demand sorbency:
4.95 1/m.sup.2 /min; equilibrium sorption: 0.66 cm.sup.3 /cm.sup.3 ; and
centrifugal retention 0.39 cm.sup.3 /cm.sup.3.
The microfiber web was divellicated as described in Insley U.S. Pat. No.
4,813,948 which is incorporated herein by reference, using a lickerin
having a tooth density of 6.2 teeth/cm.sup.2 and a speed of 900 rpm to
produce microfiber microwebs having an average nuclei diameter of 0.5 mm
and an average microweb diameter of 1.3 mm.
The microfiber microwebs (587 g) were placed in a compression mold and
compressed to form a cylindrical container having a solidity of 35%, an
outside diameter of 14.2 cm, an inside diameter of 8.0 cm, and a height of
14.6 cm and top and bottom covers, each having a diameter of 14.2 cm and a
thickness of 1.9 cm. A glass jar (0.47L capacity) containing 460 cm.sup.3
mineral oil was placed in the container, the covers were placed at the
ends of the container, and the completed container was vacuum wrapped
using 0.5 mm thick polyethylene film.
The container was tested for durability using the National Safe Transit
Association Preshipment Drop Test Procedure Project 1A for
package-products weighing under 100 pounds (45 kg) wherein the container
was subjected to falls from up to sixty inches without breakage of the
glass jar. The container was also subjected to drops onto concrete from a
height of 30 feet without breakage of the glass jar.
The container without the top cover was tested for absorbency. The cavity
of the container was filled with light mineral oil and the level
maintained at the cavity top. At time intervals as set forth in Table 1,
the oil was poured from the cavity, the container weighed, and then the
cavity refilled with oil. The rate of oil sorption and equilibrium
sorbency were determined. The data is set forth in Table 1.
TABLE 1
______________________________________
Oil Oil Sorbency
Time Weight sorbed sorbed
rate % Volume to
(min) (g) (g) (cm.sup.3)
(l/m.sup.2 /min)
saturation
______________________________________
0 587 -- -- -- --
1 761 174 210 5.1 19
2 844 257 310 3.7 29
5 990 404 487 2.4 46
10 1155 568 684 1.7 64
15 1285 698 841 1.4 78
30 1374 786 947 0.8 87
60 1414 827 996 0.4 92
120 1433 846 1020 0.2 95
1440 1473 886 1070 -- 100
______________________________________
As can be seen from the data in Table 1, the container had an excellent
sorbency rate, sorbing close to 80%of its total capacity within fifteen
minutes. The total sorption capacity of the container was about 11/8 times
the weight of the container.
EXAMPLES 2-46
In Examples 2-46, compressed particulate polyolefin microfiber materials
suitable for use in the articles and containers of the present invention
were prepared using the microfiber material and solidity indicated in
Tables 2-4. Uncompressed microfiber microweb material A was prepared
according to the procedures of Example 1. The web for microfiber material
B was prepared according to the procedures of Example 1. The web was then
introduced into a hammer mill (Champion Chop n Throw .sup..TM. Shreader,
available from Champion Products, Inc., Eden Prairie, Minn.) operating at
500 rpm to produce highly milled microfiber particles 2 to 40 mm in size,
predominantly about 10 mm in size. Material C was flash spun polyethylene
fiber having a diameter of about 1 to 5 microns and an average particle
size of 1 to 6 mm (Tywick.sup..TM. hazardous material pulp, available from
New Pig Corp., Altoona, Pa.).
EXAMPLES 2-16
In Examples 2-16, the particulate polyolefin microfiber materials were
compressed to form samples for tensile strength tests at nominal
solidities of 30%, 40%, 50%, 60%, and 70% using a hydraulic press to
compress each sample. The compressed thickness, recovered thickness (60
min after removal from the press), actual solidity and tensile strength
are reported in Table 2.
TABLE 2
______________________________________
Com-
Fiber pressed
Recovered
Actual
Tensile
Exam- Fi- weight thickness
thickness
solidity
strength
ple ber (g) (cm) (cm) (%) (KPa)
______________________________________
2 A 29.4 1.1 1.7 29.0 9.0
3 B 29.3 1.1 1.7 28.5 9.0
4 C 29.6 0.9 1.7 28.8 5.5
5 A 29.5 0.9 1.2 38.7 46.2
6 B 29.6 0.9 1.2 38.8 51.0
7 C 29.3 0.8 1.2 39.2 22.1
8 A 30.0 0.8 1.0 50.7 303.5
9 B 29.4 0.7 1.0 49.7 158.6
10 C 29.3 0.7 1.0 49.5 75.9
11 A 46.7 1.0 1.3 58.8 510.3
12 B 46.5 1.0 1.3 58.5 482.8
13 C 46.0 1.0 1.3 59.1 193.1
14 A 54.5 1.1 1.3 68.6 1034.5
15 B 54.2 1.0 1.3 69.6 965.5
16 C 54.2 1.0 1.3 69.5 310.3
______________________________________
As can be seen from the data in Table 2, increasing the solidity of the
compressed polyolefin microfiber samples increased the tensile strength of
the samples.
EXAMPLES 17-14 31
In Examples 17-31, the particles of polyolefin microfiber were compressed
to form samples for compression tests at nominal solidities of 30%, 40%,
50%, 60% and 70% using a hydraulic press to compress each sample. The
compressed thickness, recovered thickness (60 min after removal from the
press), Actual solidity and strain energy are reported in Table 3.
TABLE 3
______________________________________
Com-
Fiber pressed
Recovered
Actual
Strain
Exam- Fi- weight thickness
thickness
solidity
energy
ple ber (g) (cm) (cm) (%) (KJ/m.sup.3)
______________________________________
17 A 27.7 4.4 7.0 27.8 67.4
18 B 27.7 4.4 7.0 27.7 66.2
19 C 27.6 3.5 6.8 28.3 76.1
20 A 27.5 3.5 4.9 39.3 40.1
21 B 27.7 3.5 5.2 37.4 50.0
22 C 27.6 3.0 4.8 40.6 47.3
23 A 27.6 3.0 3.9 49.1 35.6
24 B 27.7 2.7 3.7 51.8 20.1
25 C 27.9 2.7 3.8 51.3 52.2
26 A 27.8 2.7 3.4 57.2 17.4
27 B 27.7 2.5 3.1 61.8 11.7
28 C 27.9 2.5 3.3 59.0 33.0
29 A 27.8 2.3 2.8 70.4 5.3
30 B 27.7 2.3 2.8 69.4 <5.0
31 C 27.7 2.3 2.9 67.3 22.6
______________________________________
As can be seen from the data in Table 3, as the solidity of the compressed
particles of polyolefin microfibers increases, the strain energy
decreases, indicating that as the void volume is reduced the material
becomes more rigid.
EXAMPLES 32-46
In Examples 32-46, the particles of polyolefin microfiber materials were
compressed to form samples for sorbency and retention tests at nominal
solidities of 30%, 40%, 50%, 60% and 70% using a hydraulic press to
compress each sample. The fiber weight, compressed thickness, recovered
thickness (60 min after removal from the press), and actual solidity are
reported in Table 4. The equilibrium sorption, demand sorbency and
centrifugal retention values for Examples 32-46 are reported in Table 5.
TABLE 4
______________________________________
Fiber Compressed
Recovered
Actual
weight thickness
thickness
solidity
Example Fiber (g) (cm) (cm) (%)
______________________________________
32 A 27.5 4.4 7.1 27.2
33 B 29.9 4.4 7.7 27.4
34 C 28.1 3.5 6.7 29.5
35 A 27.8 3.5 4.9 39.8
36 B 30.0 3.5 5.2 40.5
37 C 28.0 3.0 4.8 40.9
38 A 27.8 3.0 3.9 50.0
39 B 30.1 3.0 4.0 52.8
40 C 27.8 2.7 3.9 50.6
41 A 27.7 2.7 3.3 58.9
42 B 30.1 2.7 3.5 61.1
43 C 27.2 2.5 3.2 59.7
44 A 28.0 2.3 2.8 71.3
45 B 27.5 2.3 2.7 71.5
46 C 27.7 2.3 2.8 69.5
______________________________________
TABLE 5
______________________________________
Equilibrium Demand Centrifugal
sorption sorbency retention
Example (cm.sup.3 /cm.sup.3)
(l/m.sup.2 min)
(cm.sup.3 /cm.sup.3)
______________________________________
32 1.02 5.47 0.24
33 0.88 5.73 0.22
34 1.01 5.54 0.20
35 0.64 2.38 0.18
36 0.61 3.16 0.20
37 0.84 3.09 0.24
38 0.48 1.87 0.19
39 0.48 1.48 0.20
40 0.62 1.48 0.28
41 0.37 1.35 0.20
42 0.32 0.90 0.18
43 0.52 1.00 0.27
44 0.24 0.84 0.19
45 0.28 0.52 0.19
46 0.35 0.19 0.26
______________________________________
The data in Tables 4 and 5 demonstrate that as void volume is reduced in
the molded material a reduction in both equilibrium sorbency and demand
sorbency is experienced. Centrifugal retention is maintained essentially
the same regardless of solidity indicating that the effective surface area
of the materials is not reduced with densification.
EXAMPLES 47-50 AND COMPARATIVE EXAMPLES C1 AND C2
In Examples 47-50, a melt blown microfiber web was prepared and
divellicated as in Example 1 to form microfiber microwebs. Portions of the
microfiber microwebs were molded under varying amounts of pressure as set
forth in Table 6. The resulting compressed polyolefin microfiber materials
were characterized and tested for equilibrium sorption with light mineral
oil together with a sample of the melt blown microfiber web prior to
divellication (Comparative Example C1) and a sample of the microfiber
microwebs prior to compression (Comparative Example C2). The results are
set forth in Table 6.
TABLE 6
______________________________________
Fiber Molding Recovered
Actual
Equilibrium
weight pressure thickness
solidity
sorbency
Example
(g) (MPa) (cm) (%) (cm.sup.3 /cm.sup.3)
______________________________________
C1 -- -- -- 10.9 0.83
C2 -- -- -- 9.8 1.25
47 16.6 2.1 3.5 24.4 1.02
48 15.4 4.2 2.1 37.7 0.94
49 11.2 8.4 0.9 63.6 0.65
50 21.9 21.0 1.3 86.3 0.31
______________________________________
As can be seen from the data in Table 6, as the molding pressure increases,
the solidity increases and the equilibrium sorbency decreases.
EXAMPLES 51-53
In Examples 51-53, compressed polyolefin microfiber particles were prepared
as in Examples 48-50, characterized and tested for equilibrium sorption
with water. The results are set forth in Table 7.
TABLE 7
______________________________________
Fiber Molding Recovered
Actual
Equilibrium
weight pressure thickness
solidity
sorbency
Example
(g) (MPa) (cm) (%) (cm.sup.3 /cm.sup.3)
______________________________________
51 15.2 4.2 1.7 45.8 0.68
52 16.3 8.4 1.5 55.7 0.42
53 17.6 21.0 1.2 75.4 0.21
______________________________________
As can be seen from the data in Table 7, as the molding pressure increases,
the solidity increases and the equilibrium sorbency decreases.
EXAMPLES 56-58 AND COMPARATIVE EXAMPLES C3-C6
In Examples 56-58, compressed polyolefin microfiber materials were prepared
using fiber materials A, B, and C as described with regard to Examples
2-46 at a nominal solidity of 40%. The compressed thickness, recovered
thickness, actual solidity are set forth in Table 8. The materials of each
of Examples 56-58 were tested for cushion efficiency. The impact energy
density, peak acceleration and cushion efficiency are set forth in Table
9. The impact energy density and cushion efficiency reported for various
foam materials in U.S. Pat. No. 4,584,822 including a urethane ester foam
(Comparative Example C3), a polystyrene foam (Comparative Example C4), a
polyethylene foam (Comparative Example C5), and a low density polyurethane
foam (Comparative Example C6) are also reported in Table 9.
TABLE 8
______________________________________
Fiber Compressed
Recovered
Actual
weight thickness
thickness
solidity
Example Fiber (g) (cm) (cm) (%)
______________________________________
56 A 27.8 3.5 5.2 37.4
57 B 27.8 3.5 5.5 35.2
58 C 27.7 3.0 4.9 39.8
______________________________________
TABLE 9
______________________________________
Impact
energy Peak Cushion
density deceleration
efficiency
Example (KJ/m.sup.3) (g's) (J)
______________________________________
56 117 8.5 4
234 18 4.5
352 30 5
57 110 6.6 3.5
221 17 4.5
331 25 4.5
58 131 8 4
255 17 4
386 30 5
C3 117 -- 8.3
C4 117 -- 6
C5 117 -- 5
C6 117 -- 3.5
______________________________________
As can be seen from the data in Table 9, the materials of the invention
provided better cushioning efficiency than did the comparative foam
materials, except the low density polyurethane foam. Although each of the
foam materials of Comparative Examples C3-C6 provides some cushioning
effect, each of the materials is substantially non-absorbent.
EXAMPLE 59
A cylindrical container was prepared as in Example 1. The bottom cover was
placed on the cylinder and a 0.5 mm thick layer of polyethylene was
applied to the outer surface to unify the cylinder and cover and to
provide a liquid barrier. Liquid nitrogen was charged into the open
container until 450 g was imbibed and a thermocouple was placed in the
open cavity. The liquid nitrogen imbibed container was placed in a
secondary container of styrofoam having a wall thickness of 2.5 cm at an
ambient room temperature of 21.degree. C. The container was inverted after
imbibation to allow any free liquid nitrogen to escape. In the inverted
position, the temperature of the open cavity of the container was
monitored with ambient room temperature maintained at 21.degree. C. The
resulting temperatures are set forth in Table 10.
TABLE 10
______________________________________
Time Temperature
(hrs)
(.degree.C.)
______________________________________
0 -189
1 -191
2 -195
3 -192
4 -125
5 -80
6 -49
7 -27
8 -14
9 -3
10 +1
______________________________________
As can be seen from the data in Table 10, the nitrogen remained imbibed in
the container walls until it boiled off, maintaining its initial
temperature for at least three hours.
EXAMPLE 61 AND COMPARATIVE EXAMPLES C7 AND C8
A microfiber web was prepared as described in Braun U.S. Pat. No. 3,971,373
which is incorporated herein by reference, having a total basis weight of
200 g/m.sup.2 and containing 60 weight percent activated carbon (PCB
30.times.140, available from Calgon Corp.) and 40 weight percent
microfibers melt blown using polypropylene resin (Dypro.sup.198 50 MFR).
The web was divellicated as described in Example 1 to form microfiber
microwebs. The microwebs (23 g) were then compressed under 8.4 MPa
pressure in a 5.1 cm diameter mold to produce material 5.2 cm in diameter,
2.2 cm thick and having a solidity of 32% when calculated according to the
formula
##EQU2##
This molded material was then tested for carbon tetrachloride uptake
capacity. Also tested were a sample of activated carbon (Comparative
Example C7) and a sample of molded material containing no activated carbon
prepared according to the procedure of Example 26 (Comparative Example C8)
using 27.4 g microfiber microwebs to obtain material 2.7 cm thick, 4.5 cm
in diameter, and having a solidity of 57%. The results are set forth in
Table 11.
TABLE 11
______________________________________
Carbon
Sorbed Amount Sorption
sorption
weight sorbed ratio ratio
Example (g) (g) (g/g) (g/g)
______________________________________
60 31.5 8.5 0.37 0.62
C7 19.5 7.0 0.55 0.55
C8 27.5 0.1 0.004 --
______________________________________
As can be seen from the data in Table 11, the activated carbon retains
sorptive effectiveness when loaded into a microfiber web which is then
divellicated and molded. This retention of effectiveness is a result of
the open pore structure of the microfiber component and the availability
of activated carbon sorption surfaces even after molding.
EXAMPLE 61
Compressed polyolefin microfiber particulate material was prepared as in
Example 32 and tested for thermal conductivity. The thermal conductivity
was 1.5.times.10.sup.-4 cal/cm-sec-.degree. C. at a temperature of
76.degree. C.
EXAMPLE 62
Compressed polyolefin microfiber particulate material was prepared as in
Example 44 and analyzed for surface area. The surface area was 1.54
m.sup.2 /g. The surface area of the microfiber web used to prepare the
microfiber microwebs was also analyzed for surface area which was found to
be about 1.2 m.sup.2 /g. That the surface area of the compressed
polyolefin microfiber material was not significantly different from that
of the microfiber web tends to indicate that substantially no fiber
bonding occurred during the molding process.
The various modifications and alterations of this invention will be
apparent to those skilled in the art without departing from the scope and
spirit of this invention and this invention should not be restricted to
that set forth herein for illustrative purposes.
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